Cable operators, Multiple System Operators (MSO), and Digital Satellite Systems (DSS) deliver media content by utilizing satellite, Radio Frequency (RF) and Integrated Receiver and Decoder (IRD) technologies, which provide outputs that can include Asynchronous Serial Interface (ASI) signal formats. Additionally, MSOs and DSSs use dedicated hardware encoders and transcoding systems if the source video/audio is incompatible with the set top boxes of the cable or satellite operator. In general, the video/audio content delivered via the satellite to the cable or satellite operator arrives via wireless link or receiver, which is processed by an IRD that receives the stream from the satellite and can ultimately broadcast that signal to the cable operator head end in several formats. In addition, some systems may include multicast units connected with IRDs that tune to the right transponder system.
Satellite systems are used to deliver data (e.g. TV, radio, Video-on-Demand, multimedia streams) from a particular source (e.g. third-party content provider) to cable head end systems or other satellite systems. Satellite delivery is performed via a broadcast signal containing digital pictures and audio inside a transponder frequency. Transponders are radio frequency (RF) space allocated in a particular satellite.
For example, a third-party content provider can maintain multimedia files in CD/DVDs, pre-recorded storage, or as pre-recorded files that are reproduced in a particular audio or video encoding format using a video or audio encoder (e.g. MP3, H.264, AC3, and others). The audio and video is then made part of an RF signal that is broadcasted to the satellite system. This signal is then received by the cable or satellite operator using an antenna receptor and is decoded to generate either an analog signal (e.g. RCA Cables or any other analog interface) or digital signal (e.g. ASI, Asynchronous Serial Interface). If an analog signal is received, modern DVB (Digital Video Broadcasting) Cable and Satellite systems will encode this signal to their particular video/audio encoding requirements such that it can be broadcasted in digital packets via a multicast MPEG Transport Stream. The same occurs if a receiver decodes the signal in ASI. As such, this signal is converted from ASI to Ethernet, or simply redirected to a multicast MPEG Transport stream if arriving in a compatible encoding format for the receiving head end cable system.
When no satellite is being used, video, pictures and music, are read out from the DVD or a hard-drive containing MPEG-layer 3 or MPEG-layer 2 files that were encoded at a pre-determined bit rate according. Those video feeds can be reproduced at a synchronized timing using a multicast MPEG Transport Stream using RTP (Real-time Transport Protocol)-based multicast communication and RTCP (RTP Control Protocol)-based mechanisms, as well as standard UDP (User Datagram Protocol) multicast streams with proprietary timing.
Additionally, IPTV systems can provide mechanisms to broadcast a signal using the multicast protocol in MPEG transport streams to a customer premises with compatible set top boxes (same encoder, same streams, encryption keys, etc). A compatible set top box is such that when connected to the cable TV system it can properly decode video/audio from the cable operator's head end system. Some of these IPTV systems rely on CDN (Content Delivery Networks) that enable distribution of multimedia files to IP-enabled devices. For example, a mechanism can be provided whereby a head end content (MSO) that is being broadcasted to a cable subscriber is also available to an IP-enabled device such as a smartphone, PC, or tablet computer.